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USB Standby Killer Schematic Circuit Diagram

Synchronized Operation of Computer and Peripherals

The process of powering up and down a computer often necessitates a corresponding activation and deactivation of various peripherals, including printers, screens, scanners, and more. Leveraging the 5-V supply voltage available from the USB interface on the PC, all these peripherals can be conveniently synchronized with the PC’s power state. This approach is not limited to computers but can also be applied to appliances featuring a USB interface, such as modern TVs and radios. The solution, aptly named the ‘USB standby-killer,’ is a straightforward implementation, requiring only five essential components. It capitalizes on the USB output voltage to trigger the triac opto-driver (MOC3043), which incorporates zero-crossing detection.

USB Standby Killer Schematic Circuit Diagram

This, in Turn, Drives the TRIAC, Type BT126

The circuit presented here serves as a robust solution for controlling loads up to 150 W, utilizing the TRIAC, type BT126. Safeguarded by a 1-A fuse, this circuit can manage significantly larger loads with ease. However, when dealing with substantial loads or highly inductive devices, the incorporation of a snubber network becomes imperative across the TRIAC. Adjustments to the fuse rating are necessary in these scenarios. Additionally, the circuit seamlessly integrates into mains multi-way powerboards. It is crucial to prioritize the isolation between the USB and mains sections, as outlined in the Electrical Safety guidelines regularly published in this magazine.

The Role of MOC303XM and MOC304XM Devices in the Interface

The MOC303XM and MOC304XM devices play a pivotal role in this setup. They feature a GaAs infrared emitting diode optically linked to a monolithic silicon detector, effectively functioning as a zero voltage crossing bilateral TRIAC driver. Specifically engineered for integration into logic systems interfacing with equipment powered from 115 VAC lines, these devices find applications in a wide array of electronics. From teletypewriters and CRTs to solid-state relays, industrial controls, printers, motors, and consumer appliances, their versatility knows no bounds. Their adaptability ensures seamless operation in diverse electronic environments.

  • Simplifies Logic Control of 115 Vac Power
  • Zero Voltage Crossing
  • DV/DT of 2000 V/µs Typical, 1000 V/µs Guaranteed
  • To order devices that are tested and marked per VDE 0884 requirements, the suffix ”V” must be included at end of the part number. VDE 0884 is a test option. Recommended for 115/240 Vac(RMS) Applications:
  • Solenoid/Valve Controls • Temperature Controls
  • Lighting Controls • E.M. Contactors
  • Static Power Switches • AC Motor Starters
  • AC Motor Drives • Solid State Relays

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